The coins were in chronological order, indicating that they were likely uncirculated, and one of the coins was missing "In God We Trust," which historian Jack Trout tells the Chronicle indicates it was a private coin created by someone within the mint — and that it may even been created in response to the assassination of Abraham Lincoln.

However, the Chronicle previously reported that there's a problem with the mint theory — the coins range in years over decades, which would make it unlikely they came from a single heist, and there also weren't any coins from the years immediately preceding the heist. But a San Francisco Mint detective told the Chronicle that there were vaults where coins that weren't put into circulation were kept, so anything is possible.

Still, Mint spokesman Adam Stump said Tuesday that the government has done its research and can't link the couple's coins to that theft, the Associated Press reports, so they may be home-free in their plans to sell most of the coins off.

Rare coin dealer Don Kagin, who represents the couple, says they think someone in the mining industry once occupied their land and squirreled away the coins over time, according to the Associated Press.